Technical Field
The present disclosure is generally directed to laser circuits, methods and devices, and more particular, to such circuits, methods and devices including current sensing circuitry to sense a lasing current provided to a laser diode through a safety switch.
Description of the Related Art
Laser devices (e.g., devices including one or more laser diodes) are utilized in a wide range of applications. For example, such laser devices are commonly used in imaging devices, such as time-of-flight ranging devices, proximity sensing devices, gesture recognition devices and the like, in which an output of the laser device is used to detect a proximity or distance to an object, by measuring a difference in a time of emitting the laser output and a time of receiving a portion of the laser output that is reflected off of the object.
Such laser devices may pose a safety risk, for example, if the laser output power is of a level high enough to impede vision, cause injury to the eyes or skin, or the like. Accordingly, lasers are generally classified based on accessible emission limits (AELs) into various classes, which generally prescribe limitations on the output power of laser devices based on the potential hazards posed.
The output power of such laser devices thus should be monitored or at least limited such that the laser device can be safely operated, i.e., such that the laser output does not exceed the maximum output power corresponding to its class.
The output power of a laser device may be proportionally related to the lasing current provided to the laser device. As such, the output power may be deduced based on sensing the lasing current. One such technique for sensing the lasing current involves sensing the current by providing a sensing resistor in series with the load (i.e., the laser device), and sensing the current through the sensing resistor. However, the addition of a dedicated resistive sensing element complicates the laser circuitry because an additional voltage drop will be present across the sensing resistor, which impedes or otherwise affects the laser device driver operation.